/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.util;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Common place for date utils.
 * 
 * @author dac@eng.sun.com
 * @author Jason Hunter [jch@eng.sun.com]
 * @author James Todd [gonzo@eng.sun.com]
 * @author Costin Manolache
 */
public class DateTool {

	private static StringManager sm = StringManager
			.getManager("org.apache.catalina.util");

	/**
	 * US locale - all HTTP dates are in english
	 */
	public final static Locale LOCALE_US = Locale.US;

	/**
	 * GMT timezone - all HTTP dates are on GMT
	 */
	public final static TimeZone GMT_ZONE = TimeZone.getTimeZone("GMT");

	/**
	 * format for RFC 1123 date string -- "Sun, 06 Nov 1994 08:49:37 GMT"
	 */
	public final static String RFC1123_PATTERN = "EEE, dd MMM yyyyy HH:mm:ss z";

	/**
	 * Format for http response header date field
	 */
	public static final String HTTP_RESPONSE_DATE_HEADER = "EEE, dd MMM yyyy HH:mm:ss zzz";

	// format for RFC 1036 date string -- "Sunday, 06-Nov-94 08:49:37 GMT"
	private final static String rfc1036Pattern = "EEEEEEEEE, dd-MMM-yy HH:mm:ss z";

	// format for C asctime() date string -- "Sun Nov 6 08:49:37 1994"
	private final static String asctimePattern = "EEE MMM d HH:mm:ss yyyyy";

	/**
	 * Pattern used for old cookies
	 */
	public final static String OLD_COOKIE_PATTERN = "EEE, dd-MMM-yyyy HH:mm:ss z";

	/**
	 * DateFormat to be used to format dates
	 */
	public final static DateFormat rfc1123Format = new SimpleDateFormat(
			RFC1123_PATTERN, LOCALE_US);

	/**
	 * DateFormat to be used to format old netscape cookies
	 */
	public final static DateFormat oldCookieFormat = new SimpleDateFormat(
			OLD_COOKIE_PATTERN, LOCALE_US);

	public final static DateFormat rfc1036Format = new SimpleDateFormat(
			rfc1036Pattern, LOCALE_US);

	public final static DateFormat asctimeFormat = new SimpleDateFormat(
			asctimePattern, LOCALE_US);

	static {
		rfc1123Format.setTimeZone(GMT_ZONE);
		oldCookieFormat.setTimeZone(GMT_ZONE);
		rfc1036Format.setTimeZone(GMT_ZONE);
		asctimeFormat.setTimeZone(GMT_ZONE);
	}

}
